The period 1204-1259

he conquest of Constantinople by the Latins of the 4th Crusade, on April 13th 1204, forms a landmark in the history of the Byzantine State. The fall of the most important city, as a result of the expansion plans of the Western sovereigns, as well as the weakening of the Byzantium at the end of the 12th century, sealed the fall of the Byzantine Empire. The Latin conquerors, right after the fall of Constantinople, were quick to conquer the land, which was adjudicated to them by the Partitio Romaniae, and to organize their acquisition according to the feudalist standards. A new system of states was about to be created.

The Byzantine Empire was replaced by the Latin Empire of Constantinople that occupied five eighths of the land of the capital, Thrace and North-West Asia Minor. Count Baldwin of Flanders was appointed new emperor. Many small Latin states developed around the capital, which, even though they were subject to Baldwin, maintained some sort of autonomy. The most important among them were the states of Boniface of Montferrat in Macedonia and Thessaly, as well as the two Frankish hegemonies in Central Greece and the Peloponnesos, respectively. It was the Venetians who benefited most from the distribution of the Byzantine Empire. The strategic parts that served their commercial interests were passed on to the "Galenotate Democracy", whereas three eighths of the land of Constantinople also came under its control.

The new state system was completed by small independent states , which had already been formed on the eve of the 4th Crusade in Asia Minor, Rhodes and Greece. After the conquest of 1204, two more Greek states were added to the above. Those were the Empire of Nicaea, which was founded in Asia Minor by Theodore I Laskaris and the despotate of Epiros, founded by Michael I Doukas. It was to both these states, each of which claimed the title of the successor of the Byzantine Empire, which the majority of the Byzantine people fled, after the fall of Constantinople to the crusaders. So they began planning their action in order to get rid the Latins and reconquer the capital. The Empire of Nicaea was the one to finally win the title of the "exiled" Byzantine Empire and brought the capital of the state back to its natural place, in Constantinople.